An automated method for making multi-layer blanks is known from U.S. Pat. No. 4,753,699 wherein rubber layers and reinforcement layers are wound onto a rotating mandrel mounted at a fixed location. A material feed unit is moved in the longitudinal direction along the mandrel. It is disadvantageous that this manufacturing method is not continuous; instead, the method is limited to the length of the mandrel. In addition, the thickness and the angle of the wound rubber layers and reinforcement layers cannot be ensured with adequate accuracy which is required for tubular rolling-lobe flexible members for use in air springs of motor vehicles.
A winding method for continuously manufacturing reinforced tube-shaped rolling-lobe resilient members for air springs is described in DE 1 180 513. In this method, rubber layers and reinforcement layers are wound on an endless row of mandrels in series one behind the other and driven forward in an advancing direction. The tube resilient member is vulcanized on the mandrels. Thereafter, the mandrel component pieces are pulled off and releasably connected to the end of the mandrel component piece which runs into the winding machine. The precision, which is required for air spring resilient members, can disadvantageously not be ensured in the winding method. In addition, the mandrels are thermally loaded during vulcanization and the danger is present that the mandrels deform so that a uniform quality of the tubular flexible members can no longer be guaranteed.
A method and arrangement for manufacturing rubber hoses of curved shape are disclosed in U.S. Pat. No. 4,118,162. In this method, rubber layers and reinforcement layers are applied to mandrels with at least one extruder and a thread reinforcing machine with the mandrels being driven continuously in the feed direction. The mandrels abut directly and seamlessly one against the other. The continuous hose is cut into sections in a cutting device and is pulled from the mandrels and the individual mandrels are returned to the manufacturing start.
By utilizing flexible mandrels, the accuracy of the reinforced tube-shaped structure, which is required for air springs, cannot be guaranteed. In addition, with the vulcanization of the tube-shaped structures on the mandrels, the danger is present that the mandrels will distort.
For tube-shaped resilient members for use as air springs, a highly precise manufacturing is essential. Here, especially the thickness of the first rubber layer and the filament angle of the reinforcement layers is a decisive quality feature which significantly determines the characteristics of the air spring, which is manufactured from the tube-shaped resilient member, and the service life.